1. Technical Field
Illustrative embodiments described in this patent specification generally relate to a sheet discharging device and an image forming apparatus, and more particularly to a sheet discharging device including a sheet discharging unit that discharges sheets and a sheet discharge tray that stacks the sheets discharged by the sheet discharging unit, and an image forming apparatus including the sheet discharging device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet of paper, etc.) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image carrier (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
Increasing demand for smaller installation space has required greater compactness of image forming apparatuses. FIG. 1 is a vertical cross-sectional view illustrating a configuration of an image forming apparatus 110 of the related art. The image forming apparatus 110 includes a sheet feed tray 101 storing recording media such as sheets of paper, a sheet feed roller 102 provided downstream from the sheet feed tray 101 in a direction of conveyance of the sheet, a pair of conveyance rollers 103 provided downstream from the sheet feed roller 102 in the direction of conveyance of the sheet, image forming units 104Y, 104M, 104C, and 104K (hereinafter collectively referred to as image forming units 104) each forming a toner image of a specific color, that is, yellow, magenta, cyan, or black, on the sheet, conveyance belt 105 provided below the image forming units 104, an irradiating device 106 that irradiates photoconductors included in the image forming units 104, a fixing device 107 that fixes the toner image onto the sheet using heat, a sheet discharge tray 108 onto which the sheet having the fixed image thereon is discharged from the image forming apparatus 110, a pair of discharging rollers 109 that conveys the sheet having the fixed image thereon to the sheet discharge tray 108, and so forth. A sheet stored on the sheet feed tray 101 is fed forward by the sheet feed roller 102 and is conveyed to the conveyance belt 105 through the pair of conveyance rollers 103. While the sheet is being conveyed by the conveyance belt 105, toner images formed on the photoconductors included in the image forming units 104 are sequentially transferred onto the sheet and superimposed one atop the other so that a full-color toner image is formed on the sheet. The sheet having the full-color toner image thereon is then conveyed to the fixing device 107 to fix the full-color toner image onto the sheet with heat and pressure. Thereafter, the sheet having a fixed full-color image thereon is discharged from the image forming apparatus 110 through a discharging opening by the pair of discharging rollers 109 and is stacked on the sheet discharge tray 108.
The sheet discharge tray 108 is hinged along one edge and attached to the image forming apparatus 110. Accordingly, the sheet discharge tray 108 is opened to an extended position as illustrated by broken lines in FIG. 1 to stack the sheet discharged from the image forming apparatus 110. By contrast, with the sheet discharge tray 108 in a closed position as illustrated by solid lines in FIG. 1 the sheet discharge tray 108 is flush with the exterior of the image forming apparatus 110. In those image forming apparatuses in which a conveyance path of a sheet is almost straight from a sheet feed tray to a sheet discharge tray such as the image forming apparatus 110, the sheet discharge tray is usually provided on either front or back side surfaces of the image forming apparatuses. For example, the image forming apparatus 110 shown in FIG. 1 has the sheet discharge tray 108 provided on a front surface thereof. Consequently, an installation space required for the image forming apparatus 110 is increased to the front by the length of the sheet discharge tray 108.
In addition, the sheet discharge tray 108 must have a size sufficient for stacking the sheet, which in turn increases the space required for the sheet discharge tray 108. In order to reduce the space for the sheet discharge tray 108, an opening may be provided at a portion of the sheet discharge tray 108 facing a main body of the image forming apparatus 110, and the sheet is discharged from the image forming apparatus 110 through the opening and into the sheet discharge tray 108 while the sheet discharge tray 108 is closed. Such a configuration allows a user to use the image forming apparatus 110 without having to open the sheet discharge tray, thereby reducing the installation space for the image forming apparatus 110.
The above-described arrangement can work well in a case in which images are formed on only several sheets of paper, because the sheet discharge tray 108 does not need to be opened. The sheets discharged from the image forming apparatus 110 through the opening may be manually received by the user and directly stacked on a desk positioned next to the image forming apparatus 110, or the like.
One example of a related-art image forming apparatus includes a sheet discharge tray having an opening or a cutout therein with a width greater than the maximum width of a sheet of paper used in the image forming apparatus. The sheet discharge tray is rotatably provided near a discharging opening of the image forming apparatus from where the sheet is discharged to stack the sheet thus discharged. The opening or the cutout is positioned outside a conveyance path of the sheet discharged from the discharging opening of the image forming apparatus when the sheet discharge tray is in a first position protruding from the image forming apparatus to stack the sheet discharged from the image forming apparatus. By contrast, the opening or the cutout is positioned corresponding to the discharging opening when the sheet discharge tray is in a second position folded toward the image forming apparatus.
However, a problem with the above-described arrangement is that the sheet stacked on the sheet discharge tray in the first position may drop through the opening or the cutout. Further, a leading edge of the sheet discharged from the image forming apparatus may get stuck or jammed in the opening.
In another approach, to reduce the space required for the apparatus the sheet discharge tray is fixedly mounted at an angle to a substantially straight conveyance path of the sheets. The sheet discharge tray has an opening that can be covered or closed by a plate. The opening lies on a virtual line representing an extension of the conveyance path of the sheets. The sheets are discharged through the opening.
However, because the above-described sheet discharge tray is not rotatable but is fixed at an angle to the image forming apparatus, this configuration is not applicable to a sheet discharge tray having a shutter that is openably closed in conjunction with rotation or opening and closing of the sheet discharge tray.